Quantum Gravity

This book seeks to present a new way of thinking about the interaction of gravitational fields with quantum systems. Despite the massive amounts of research and experimentation, the myriad meetings, seminars and conferences, all of the articles, treatises and books, and the seemingly endless theorization, quantization and just plain speculation that have been engaged in regarding our evolving understanding of the quantum world, that world remains an enigma, even to the experts.

Three years have passed after the First Moscow Seminar on Quantum Gravity. It is a rather long time interval for the modern theoretical physics. The talks given at the present Second Seminar which took place in October 13-15, 1981 in Moscow contain the discussion of new results obtained during this period and the problems which arose. More than one hundred Soviet scientists and a number of the foreign guests attended this Seminar, which as the previous one was held by the Nuclear Physics Department of the Academy of Sciences of the USSR and the Institute for Nuclear Research of the Academy of Sciences of the USSR.

This second edition offers a comprehensive introduction to loop quantum gravity (LQG) in self-dual variables, including the necessary prerequisites. Additionally, it delves into various significant research areas that have emerged in recent years. New content (including an entirely new chapter dedicated to dynamics of quantum spacetime) explores the description of spin networks and spin-foams, their historical development as well as connections to tensor networks, BF theory, and emerging approaches including the spinorial representation of LQG, SU(2) coherent states, and group field theory. Furthermore, the book provides expanded appendices covering essential tools and concepts, such as the connection between information theory and entropy, and overviews of group theory and differential geometry. All topics are presented from a non-expert perspective, ensuring self-containment and accessibility. The primary aim of this second edition remains helping researchers, bewildered by the vast array of topics within this rapidly growing field of quantum gravity, to gain a fundamental understanding of the current developments.